TWI736101B - Photomask assembly with reflective photomask and method of manufacturing a reflective photomask - Google Patents

Abstract

A photomask assembly (900) includes a reflective photomask (100) and a protection structure (200). The reflective photomask (100) includes a substrate (110) and a reflective multilayer (120) on a first substrate surface (111) of the substrate (110) at a front side of the reflective photomask (100). The protection structure (200) on a second substrate surface (112) of the substrate (110) at a backside of the reflective photomask (100) is detachable from the reflective photomask (100) at a temperature below 150 degree Celsius.

Description

Photomask assembly with reflective photomask and manufacturing of reflective photomask Construction method

The present disclosure relates to a photomask assembly with a reflective mask, in particular to a photomask assembly with EUV (Extreme Ultraviolet) photomask, and a photomask assembly with a reflective mask blank (reflective mask blank) . This disclosure is more about the manufacturing method of the reflective photomask.

Extreme ultraviolet lithography (EUVL) uses electromagnetic radiation with an exposure wavelength of about 13.5nm. It is a promising next-generation lithography technology that can be used to manufacture semiconductor devices on a large scale. Its resolution exceeds 193nm. The resolution achievable by lithography. Ultra-ultraviolet lithography uses reflective optics and reflective photomasks with multilayer mirrors. Generally, during exposure of the semiconductor wafer, an electrostatic chuck empty chuck holds the photomask in place. Defects on the back side of the photomask, such as particles accidentally sandwiched between the suction cup and the backside of the photomask, may affect the flatness of the front side of the photomask, may cause unexpected image shift and focus errors, and may damage the suction cup.

The purpose of the embodiments is to reduce the frequency of serious defects on the back side of the photomask or to reduce them completely.

The purpose of the present invention is achieved through the subject-matter of an independent item. Attached items indicate other embodiments.

The disclosed embodiment relates to a photomask assembly, which includes a reflective photomask and a protective structure. The reflective photomask includes a substrate and a reflective multilayer on the first substrate surface of the substrate on the front side of the reflective photomask. At a temperature lower than 150° C., the protective structure on the second substrate surface of the substrate on the back side of the reflective photomask can be separated from the reflective photomask.

Another embodiment of the present disclosure relates to a manufacturing method of a reflective photomask. The method includes forming a reflective photomask including a substrate, a reflective multilayer on a first substrate surface of the substrate, and an absorber pattern on the reflective multilayer on a front side of the reflective photomask. Before forming the absorber pattern, a protective structure is combined on the second substrate surface of the substrate on the back side of the reflective photomask.

Another embodiment of the present disclosure relates to another photomask assembly, which includes a reflective photomask and a protective structure. The reflective photomask includes a substrate, a reflective multilayer on the first substrate surface of the substrate, and an absorber pattern on the reflective multilayer on the front side of the reflective photomask. At a temperature lower than 150° C. and/or by applying an inert treatment liquid to the absorber pattern, the protective structure on the second substrate surface of the substrate on the back side of the reflective photomask can be removed from the reflective photomask.

Another embodiment of the present disclosure relates to another method of manufacturing a reflective photomask. Form a reflective photomask, the reflective photomask includes a substrate and the front of the reflective photomask Reflective multilayer on the surface of the first substrate on the side of the substrate. Before forming the absorber pattern on the reflective multilayer, a protective structure is provided on the second substrate surface of the substrate on the back side of the reflective photomask. After forming the absorber pattern, the protective structure is removed.

The drawings are included to provide a further understanding of the embodiments, and the drawings are incorporated into this specification and constitute a part of this specification. The drawings illustrate the embodiments of the present disclosure, and together with the embodiments are used to explain the principles of the embodiments. By referring to the detailed description below, other embodiments and expected advantages will become better understood, so it will be easier to understand them.

100: reflective mask

101: The first major surface

102: second major surface

103: side surface

104: surface normal

105: surface part

110: substrate

111: The first substrate surface

112: Second substrate surface

114: dorsal membrane

115: The main part of the substrate

119: Conductive interface layer

120: reflective multilayer

121: first layer

122: second layer

129: Overlay

130: absorber pattern

131: Buffer layer

134: Absorber layer stack

135: Absorber layer

139: Anti-reflective layer

180: frame groove

191: pattern part

192: Frame part

200: Protective structure

203: side surface

220: Adhesive layer

221: Adhesive

230: main carrier

240: Flexible tape

300: mechanical adapter

303: Contour

310: receiving port

900: Mask assembly

B: End of section line

d1: thickness

d2, d3: horizontal size

r1: radius

Figures 1A~1B show a schematic plan view and a schematic vertical cross-sectional view of a photomask assembly according to an embodiment. The photomask assembly includes a reflective photomask and a protective structure on the back side of the photomask; Figures 2A~2B Shows a schematic vertical cross-sectional view of a photomask assembly including a reflective photomask and a protective structure on the back side of the photomask according to other embodiments; Figures 3A to 3C show a reflective photomask without a conductive back A schematic vertical cross-sectional view of the photomask assembly of the side film; Figures 4A to 4C show a schematic vertical cross-sectional view of the photomask assembly with a reflective photomask and a conductive back side film; Figures 5A to 5B show that A schematic plan view and a schematic cross-sectional view of the photomask assembly of the adapter; and Figures 6A to 6D show a schematic view of a part of the reflective photomask and the protective structure The vertical cross-sectional view is used to show the manufacturing method of the reflective photomask according to another embodiment.

In the following detailed description, reference is made to the drawings forming a part thereof, and specific embodiments are illustrated in the drawings, in which the reflective photomask, the reflective photomask manufacturing method, and the semiconductor device The manufacturing method can be practiced. It should be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. For example, features illustrated or described for one embodiment can be used on or in combination with other embodiments to produce yet another embodiment. This disclosure is intended to include such modifications and changes. The examples are described in specific language and should not be construed as limiting the scope of the attached patent application. These drawings are not drawn to scale and are for illustration purposes only. If not otherwise specified, corresponding elements are represented by the same element symbols in different drawings.

The terms "having", "including", "including/comprising", etc. are open-ended, and these terms indicate the existence of the stated structure, element or feature, but do not exclude other elements or features. Unless the context clearly indicates otherwise, the articles "a", "an" and "the" are intended to include the plural and singular.

In addition, the term "on" should not be interpreted as simply meaning "directly on". Rather, if one element is "on" another element, for example, if a layer is "on" another layer or "on" a substrate, then another element (eg, another layer) can be located between the two elements. For example, if this layer is "on" the substrate, another layer can be placed between this layer and the substrate.

The main component of a layer or structure composed of a compound or an alloy is an element whose atoms form a compound or an alloy. For example, nickel and silicon are the main components of the nickel silicide layer, while copper and aluminum are the main components of copper-aluminum alloy.

The term "metal/metallic" used in the context of this application does not include semi-metal. In particular, the term "metal" does not include the elements boron, silicon, germanium, arsenic, antimony, and/or tellurium. The metal structure includes at least a metal part, and in addition to the metal part, may also include another part or other parts from a non-metallic material or from a semi-metallic material. Transition metals are chemical elements with atomic numbers 21 to 30, 39 to 48, 57 to 80, and 89 to 112.

According to an embodiment, the photomask assembly includes a reflective photomask and a protective structure. The reflective photomask may include a substrate and a reflective multilayer on the first substrate surface of the substrate, wherein the multiple layers are formed on the front side of the photomask. The protection structure is arranged on the second substrate surface of the substrate on the back side of the photomask, and can be separated from the photomask at a temperature lower than 150°C.

The substrate may include the main part of the substrate from Low Thermal Expansion (LTE) material, and the coefficient of thermal expansion is less than 1 ppm/K. In addition to the main part of the substrate, the substrate may also include one or more other layers on the side of the main part of the substrate facing the reflective multilayer and/or on the side of the main part of the substrate averted from the reflective multilayer. One or more other layers.

The reflective multilayer may include a plurality of layer pairs, where each layer pair includes a first layer and a second layer. At the exposure wavelength, the first layer has a first refractive index and the second layer has a second refractive index. Different reflectivity of the first and second layers The resulting reflective multilayer is effective as a Bragg reflector, the maximum reflectance of which is typically equal to or close to the exposure wavelength of extreme ultraviolet (EUV) or beyond (beyond EUV). For example, the exposure wavelength may be 13.5 nm or 6.7 nm. The reflective multilayer may include one or more other layers on the side facing the substrate and/or on the side remote from the substrate.

The photomask may further include an unpatterned continuous absorber layer stack or a patterned absorber layer stack on the reflective multilayer, wherein the patterned absorber layer stack forms an absorber pattern, The absorber pattern may have openings exposing the partially reflective multilayer. The absorber layer stack may include at least one absorber layer, the absorber layer having an absorbance of at least 40% at an exposure wavelength of, for example, 13.5 nm or 6.7 nm. The absorber layer stack may include one or more other layers on the side facing the reflective multilayer and/or on the side remote from the reflective multilayer.

The protective structure may be a flexible tape or rigid plate including at least one of glass, metal, semiconductor material (for example, crystal or polysilicon), ceramic, sintered material, and rigid resist. The protective structure may cover the entire surface of the second substrate. The protective structure and the outer surface of the photomask may be flush. Alternatively, the protective structure may project laterally beyond the outline of the photomask.

The protective structure may be bonded to the substrate. The bonding between the protective structure and the substrate may be an adhesive bonding or a glueless bonding. For example, the protective structure and the photomask can be directly combined. The adhesion between the directly bonded protective structure and the photomask can be based on chemical bonds, hydrogen bonds, metal bonds, ions and/or co-bonds between the substrate 110 and the protective structure 200. Valence bond. Direct bonding may include applying moderate mechanical force to press the protective structure and the photomask to each other, and at least one of the two bonding surfaces or a combination thereof at a moderate temperature below 100°C (for example, 120°C) Heat treatment is performed, for example, fusion bonding, thermo-compressive bonding, and bonding by atomic rearrangement.

The protective structure can be separated from the mask at a temperature below the boundary temperature, at which the atoms in the mask stack (for example, in a reflective multilayer) begin to diffuse across the interface of the layer into the adjacent layer (more than Negligible degree). For example, the protective structure may be separable at a temperature below 150°C (e.g., at most 135°C or at most 120°C). The separation may include debonding the bond between the protective structure and the photomask. The separating protection structure may further include cleaning the surface of the second substrate with a rinse fluid that is inert to the material of the absorber layer stack and the reflective multilayer. For example, the flushing fluid includes liquid, gas, or both.

The protective structure that can be separated from the photomask at a temperature lower than 150°C can be easily removed from the reflective photomask without adversely affecting the photomask, especially the absorber pattern and reflective photomask. The multilayer and/or second substrate surface has a negative impact.

In particular, in such a way that none of the absorber pattern, the reflective multilayer, and the substrate will be affected more than a negligible degree, and no non-negligible residue will be left on the surface of the second substrate, The protective structure can be removed.

In other words, after the protective structure is removed, the surface of the second substrate can still meet the general specifications on the back side of the extreme ultraviolet (EUV) mask regarding flatness and flatness. In particular, the protective structure did not leave the surface of the second substrate protruding beyond Residual particles of 10μm. In addition, after the protective structure is removed, the size of the absorber pattern and multilayer meets the general specifications of the absorber pattern and multilayer and the specific specifications of certain mask layouts.

The protective structure can be removed before the reflective photomask is installed in the ultra-ultraviolet lithography (EUVL) equipment or before the photomask is shipped to the semiconductor factory.

The protective structure may be used during the processing of the front side of the photomask (e.g., during the deposition of the reflective multilayer, during the deposition of the absorber layer stack, and/or during the patterning process of the absorber layer stack, or during the formation of a frame trench (frame trench). During the trench), temporarily protect the photomask from particle contamination. The removal of the protective layer includes removing particles deposited on the back side of the photomask before and/or during the front side processing of the reflective photomask. Even particles deposited before applying the protective structure that have not been completely removed by the previous washing process but still adhere to the protective layer can be removed together with the protective structure.

In addition, the protective structure can avoid direct contact between the mask processing tool and the back side of the photomask, and in this way can protect the backside of the reflective photomask from mechanical damage, such as scratches.

Known tools and methods of semiconductor wafer technology can be used to provide the protective structure. For example, the protective structure may include temporarily fixed to the semiconductor wafer during wafer thinning, wafer grinding, wafer dicing, and/or wafer probing. That kind of rigid carrier or flexible tape.

According to an embodiment, the substrate may include a backside film that may form a surface of the second substrate. The backside film may be a conductive film, which helps the electrostatic chuck of the reflective photomask in the ultra-ultraviolet lithography device. For example, the backside film may include chromium (Cr) and nitrogen (N), or may include tantalum (Ta) and boron (B). The protective structure can be directly bonded to the back side film. For example, electrostatic chucking on a nail-bed chuck can reduce the adverse effects of unevenness and/or roughness on the back side. Alternatively, the protective structure may be directly formed of a low thermal expansion material on the main part of the substrate.

According to an embodiment, the protective structure may be detachable, for example, by applying a temperature between 110°C and 150°C, by applying electromagnetic radiation, by applying a de-bonding fluid that releases the bond (de-bonding). fluid) and/or by applying moderate mechanical force, the protective structure can be separated from the photomask. A moderate mechanical force should be understood as a mechanical force weak enough that it will not cause damage to the photomask. The moderate mechanical force can be in the range of the force that can be applied by human hands or lower.

For example, the heat treatment can peel off (ie, completely release or weaken at least 90%) the bonding force between the protective structure and the photomask. For example, a flow of hot air may be directed to the back side of the photomask assembly, and during/after the heat release/weakening of the bonding force, the protective structure may be mechanically peeled off. At a peeling temperature greater than 110° C., it is still possible to reliably keep the protective structure fixed to the photomask during the front-side processing of the photomask (for example, during all processes of patterning the absorber layer stack). When the peeling temperature is lower than 150°C, for example, at most 135°C or at most 120°C, the peeling process will not affect the front side of the photomask (for example, the absorber pattern).

Alternatively or in addition, by irradiating the protective structure with electromagnetic radiation in a certain wavelength range (for example, ultraviolet light (UV light)), at least 90% of the binding force between the photomask and the protective structure can be completely released or weakened.

Alternatively or in addition, by applying a suitable peeling fluid (for example, a fluid containing a solvent for bonding), at least 90% of the bonding force between the photomask and the protective structure can be completely released or weakened.

According to an embodiment, the protective structure may include a main carrier and an adhesive layer reversibly bonding the main carrier to the reflective photomask.

Generally, releasing a reversible bond leaves the reversible bond structure undamaged. More specifically, releasing the reversibly bonded master carrier from the photomask keeps both the photomask and the master carrier intact. A photomask that meets the predetermined requirements before releasing the reversible key, at least after a further cleaning step, will meet the same requirements (if applicable) after releasing the reversible key. The master carrier released from the reversible bond can be used for the same purpose (if applicable) without functional limitation, at least after a further cleaning step.

The main carrier may be a rigid carrier made of a solid material (for example, a continuous, unpatterned plate or a plate with dents, where the dents may expose a part of the surface of the second substrate). For example, the main carrier may have the shape of a framed grid, or may be a frame formed along the edge of the photomask.

The adhesive layer may include an adhesive applied on the mounting surface of the main carrier, applied on the surface of the second substrate, or both before adhering the main carrier to the surface of the second substrate. Alternatively, the adhesive layer may be an adhesive foil inserted between the main carrier and the surface of the second substrate before bonding the main carrier to the second surface.

If applicable, the rigid main carrier can be reused after a further cleaning process to remove residues from the adhesive layer. By using a reusable main carrier, a relatively expensive protective structure can be used without substantial increase in cost. In the case of wafer back grinding, wafer dicing, and/or wafer probing, it has been proven and tested without residual glue and adhesive foil in the manufacturing process of semiconductor wafers.

According to an embodiment, the protective structure may include a carrier tape and an adhesive layer for adhering the carrier tape to the photomask. The carrier tape may be any tape used in semiconductor manufacturing to temporarily stabilize semiconductor wafers, for example, during grinding, dicing, and/or probing. Alternatively, the carrier tape may be any tape used as a pick-up tape.

For example, the protective structure is UV tape, which has a strong bonding strength immediately after bonding. In at least some front-side manufacturing processes, UV tape covers the backside of the mask. By irradiating with ultraviolet light, the bonding strength is reduced by at least 90%, and the mask can be easily removed from the ultraviolet tape after ultraviolet irradiation.

According to an embodiment, the photomask assembly may include a mechanical adaptor, and the mechanical adaptor includes a receiving port adapted to support the reflective photomask. The contour of the mechanical adapter corresponds to the standard wafer contour. For example, the contour of the mechanical adapter may correspond to the contour of a standard wafer with a diameter of 200 mm or 300 mm. The mechanical adapter facilitates the use of tools that bond the rigid master carrier and/or carrier tape to the semiconductor wafer to bond this carrier to the reflective photomask. For example, a mechanical adapter can facilitate the second base of the photomask in the laminator tool A back-grind tape or pick-up tape is applied to the surface of the board, because the mechanical adapter is usually used to laminate semiconductor wafers with back-grind tape, dicing tape, or pick-up tape.

According to an embodiment, a method for manufacturing a reflective photomask may include forming a reflective photomask, the reflective photomask including a substrate, a reflective multilayer on a first substrate surface of the substrate, and a multilayer on the front side of the photomask. Absorber pattern. Before patterning the absorber pattern, the protective structure may be bonded to the surface of the second substrate on the back side of the photomask.

The combination of the protective structure to the photomask can allow the peeling of the protective structure, and therefore, the temporary protection of the backside of the photomask will not adversely affect the photomask.

According to an embodiment, the protective structure may be separated from the photomask at a temperature lower than 150°C, wherein the separation of the protective structure from the photomask may include peeling of the bond between the protective structure and the photomask, and wherein the peeling may include bonding to The binding force of mechanical peeling is completely released or the binding force is weakened by at least 90%. When the peeling temperature is lower than 150°C (for example, at most 135°C or at most 120°C), the peeling process does not affect the front side of the photomask (for example, the absorber pattern).

A protective structure can be provided before forming the reflective multilayer, wherein the protective structure can avoid particle contamination on the surface of the second substrate during and in between all related deposition processes. Alternatively, the protective structure may be provided after forming the reflective multilayer and before depositing the absorber layer stack forming the absorber pattern, wherein the protective structure can avoid the second step during and between all processes for forming the absorber pattern. Particle contamination on the surface of the substrate.

According to an embodiment, the protective structure can be separated from the photomask after the absorber pattern is formed. The protective structure provides temporary protection to the back side of the photomask without affecting the use of the photomask in the ultra-ultraviolet lithography equipment.

According to another embodiment, the photomask assembly may include a reflective photomask and a protective structure. The reflective photomask may include a substrate, a reflective multilayer on the first substrate surface of the substrate, and an absorber pattern on the multilayer, wherein the multilayer and the absorber pattern are formed on the front side of the photomask. The protective structure is provided on the second substrate surface of the substrate on the back side of the photomask, and can be removed from the photomask at a temperature lower than 150° C. and/or by applying a processing liquid that is at least inert to the absorber pattern. The treatment liquid may also be inert to the reflective multilayer and/or substrate. The treatment liquid may include a solvent-based fluid.

The protective structure can be removed at a temperature lower than 150°C and/or by applying a treatment solution that is inert to the absorber pattern. The mask can be mechanically contacted with the mask processing tool to provide temporary protection for the mask to prevent Contamination and/or defects on the back side. Temporary protection may not adversely affect the use of photomasks in ultra-ultraviolet lithography equipment, especially the absorber pattern, reflective multilayer, and/or the surface of the second substrate.

According to an embodiment, the reflective photomask includes a backside film directly formed on the surface of the second substrate. The backside film may be a conductive film, which contributes to the electrostatic chuck of the reflective photomask in the ultra-ultraviolet lithography apparatus. For example, the backside film may include chromium (Cr) and nitrogen (N), or may include tantalum (Ta) and boron (B). The protective structure can be directly formed on the backside film. The electrostatic chuck on the nail bed chuck can reduce the adverse effects of unevenness and/or roughness on the back side. Alternatively, the protective structure may be directly formed of a low thermal expansion material on the main part of the substrate.

The protective structure can be removed chemically or physically, for example, by grinding, chemical mechanical polishing (CMP), mechanical polishing, or physical dry etching. For example, reactive ion etching (RIE) or ion beam etching (Ion Beam Etching, IBE) can be used to remove protective structures _{based on oxides and/or silicon compounds (such as Si 3} N ₄ or Si _{2 O)} .

According to another embodiment, the protective structure may be formed of a material that is completely soluble in a dissolver fluid.

For example, the protective structure may be composed of one or more polymeric materials, or may include one or more polymeric materials in addition to non-polymeric materials, where the dissolving agent fluid may be a liquid containing an organic solvent. For example, the polymer material may include polyimide or polytetrafluoroethylene (PTFE).

According to another example, the protective structure may include at least one of a metal layer, an oxide layer, and a layer formed of a silicon compound, wherein the dissolving agent fluid may include an acid-containing liquid. In the case where the photomask includes a metal backside film, the dissolving agent fluid may include an etchant that removes the protective structure with high selectivity with respect to the backside film. For example, the protective structure may include a titanium (Ti) layer, an aluminum (Al) layer, a layer including titanium (Ti) and/or aluminum (Al), a silicon oxide layer (for example, using tetraethoxysilane (TEOS) as a precursor) At least one of a silicon dioxide (Si ₂ O) layer and a silicon nitride (Si ₃ N ₄ ) layer formed of materials.

According to another example, the dissolving agent fluid is an activated etching gas, which dissolves the protective structure _{based on oxide and/or silicon compound (such as Si 3} N ₄ or Si _{2 O) during the plasma etching process.}

According to an embodiment, the protective structure can be sprayed onto the surface of the second substrate, wherein the protective structure can be applied in a simple and cost-effective manner. In the manufacturing process of the photomask, the requirements on the backside flatness and/or backside flatness of the photomask and the protective structure are relatively loose, and therefore can be achieved by a cost-effective spraying method.

Another embodiment of the present disclosure relates to another method of forming a reflective photomask. The present disclosure provides a photomask. The photomask may include a substrate and a reflective multilayer on the first substrate surface of the substrate on the front side of the photomask. Before forming the absorber pattern on the multilayer, a protective structure is provided on the surface of the second substrate of the substrate on the back side of the photomask. After forming the absorber pattern, the protective structure may be removed. The protective structure provides effective temporary protection for the back side of the mask to prevent particle contamination and mechanical defects caused by, for example, mask handling tools.

According to an embodiment, the protective structure can be removed from the photomask at a temperature of at most 150° C. and/or by applying a treatment liquid that is inert to the absorber pattern. The protective structure can be applied and removed in a simple and cost-effective manner.

According to another embodiment, the protective structure can be separated from the photomask, wherein the application and removal of the protective structure can be proven and tested using a process combined with grinding, cutting, and/or probing of a semiconductor wafer, or used for a pick-up process.

Figures 1A to 1B show the photomask assembly 900, which has a reflective photomask 100 and a protective structure 200 for the exposure wavelength in the range of 1nm to 15nm. example For example, the reflective photomask 100 may be an ultra-ultraviolet lithography mask for an exposure wavelength of about 13.5 nm. According to another embodiment, the reflective photomask 100 may be used for a beyond extreme ultraviolet lithography (BEUVL) mask with an exposure wavelength in the range of 1 nm to 10 nm (for example, about 6.7 nm).

The reflective mask 100 may have an approximately rectangular shape with an edge length of several centimeters. The pattern portion 191 of the reflective photomask 100 includes an image to be projected on the semiconductor wafer, wherein the pattern portion 191 includes image signals of a single semiconductor device or a plurality of semiconductor devices. The frame part 192 may laterally surround the pattern part 191. The frame portion 191 does not include image signals related to the semiconductor device. The frame part 191 may include a frame groove 180 extending from the first main surface 101 into the reflective photomask 100.

During the exposure of the semiconductor wafer in the ultra-ultraviolet lithography apparatus, the photomask 100 is fixed on the mask stage, wherein the photomask 100 can be held on the back side of the reflective photomask 100 on the mask stage by the second master. The surface 102 is stuck. The exposure radiation impinges on the first main surface 101 on the front side of the photomask 100. A portion of the exposure radiation reflected on the first main surface 101 encodes the image information projected into the photoresist layer, which covers the semiconductor wafer during exposure.

The second main surface 102 on the back side of the reflective photomask 100 is flat and flat. The direction parallel to the second main surface 102 is the lateral direction. The first main surface 101 may include a surface portion 105 parallel to the second main surface 102. The surface normal 104 defines a vertical direction for the surface portion 105 parallel to the second main surface 102.

The reflective photomask 100 includes a substrate 110, and the substrate 110 includes at least a main part of the substrate made of a low thermal expansion material. The substrate 110 may include additional layers, For example, a backside film on the backside of a low thermal expansion material. The second substrate surface 112 of the substrate 110 forms the second main surface 102 of the reflective photomask 100.

The reflective multilayer 120 is formed on the first substrate surface 111 on the front side of the substrate 110. The reflective multilayer 120 may include a plurality of layer pairs, where each layer pair includes a first layer 121 and a second layer 122. The first layer and the second layer have different refractive indices. For example, the first layer 121 may be a molybdenum (Mo) layer with a thickness of 2 nm to 5 nm, and the second layer 122 may be a silicon (Si) layer with a thickness of 2 nm to 5 nm. The number of layer pairs can be between 20 and 70. The different indicators of reflection of the first and second layers 121, 122 result in the reflective multilayer 120 being effectively used as a Bragg reflector, with maximum reflection at a predetermined exposure wavelength (for example, 13.5nm or 6.7nm) . The minimum reflectivity of the reflective multilayer 120 at the exposure wavelength is at least 50%, for example, greater than 60%.

The absorber pattern 130 is formed on the side of the reflective multilayer 120 away from the substrate 110 such that the reflective multilayer 120 is between the absorber pattern 130 and the substrate 110. The absorber pattern 130 may have an absorption rate of at least 50% at the exposure wavelength. The thickness of the absorber pattern 130 may be in the range of 10 nm to 90 nm. The absorber pattern 130 may be formed by a stack of absorber layers including at least one absorber layer, wherein the absorber layer may be based on a metal nitride, for example, a transition metal nitride like tantalum nitride (TaN) or titanium nitride (TiN). For example, the absorber layer may be based on tantalum nitride, tantalum nitride may contain other main components, such as boron (B) or oxygen (O), wherein the absorber layer is a tantalum boron nitride (TaBN) layer or a boron tantalum oxide (tantalum boron oxide, TaNO) layer. Alternatively, the absorber layer may contain chromium (Cr). For example, the absorber layer can be composed of chromium nitride (CrN) or contain Chromium Nitride (CrN). The frame groove 180 may extend through the reflective multilayer 120 to reach or enter the substrate 110.

The protection structure 200 is arranged on the back side of the photomask 100. The protection structure 200 may be directly formed, for example, deposited on the second substrate surface 112, or may be bonded to the second substrate surface 112. The side surface 203 of the protection structure 200 may be flush with the side surface 103 of the reflective mask 100. If the protective structure 200 is combined with the reflective photomask 100, the thickness d1 of the protective structure 200 can be in the range of 50 μm to 2000 μm (for example, 80 μm to 1000 μm), if the protective structure 200 is directly formed (for example, deposited on the photomask 100), Then, the thickness d1 of the protection structure 200 may be in the range of 0.1 μm to 30 μm.

The protective structure 200 may include a single layer or at least two different structures, for example, a rigid carrier or a flexible tape and an adhesive layer for adhering the rigid carrier or flexible tape to the photomask 100.

FIG. 2A shows a photomask assembly 900 with an absorber pattern 130 and no frame grooves.

The photomask assembly 900 of FIG. 2B includes a reflective photomask 100 with an unpatterned absorber layer stack 134. In other words, the reflective mask 100 represents a mask blank in a state before the absorber pattern is formed by patterning the absorber layer stack 134.

FIGS. 3A to 3C relate to the reflective mask 100 without a backside film. In all the drawings, the protective structure 200 is directly formed on the surface of the main part 115 of the substrate by a low thermal expansion material.

The absorber pattern 130 is formed by an absorber layer stack, which includes an absorber layer 135 and a buffer layer 131 formed between the absorber layer 135 and the reflective multilayer 120, wherein the buffer layer 131 can be effectively used during the formation of the absorber pattern. As an etch stop layer. Alternatively or in addition to the buffer layer 131, the absorber layer stack may include an anti-reflective layer 139 located on the front side of the absorber layer 135.

At inspection wavelengths that are generally longer than the extreme ultraviolet inspection wavelength, the reflectance of the anti-reflection layer 139 is smaller than that of the absorber layer 135. The anti-reflective layer 139 may include a metal nitride or may be composed of a metal nitride, such as a transition metal nitride (such as titanium nitride or tantalum nitride), and may include one or more selected from chlorine , Fluorine, argon, hydrogen or other components of the group of oxygen. The anti-reflection layer 139 may be formed by treating the surface of the absorber layer 135 in an environment containing other components or their precursors. According to another embodiment, the anti-reflection layer 139 may be a silicon nitride layer or may be formed of tantalum oxide, which may contain other main components (such as boron), or may be a material containing chromium (such as chromium oxide (CrO)). )).

The reflective multilayer 120 may include a cover layer 129 located on a side away from the substrate 110. The capping layer 129 may be a layer composed of ruthenium (Ru) or containing ruthenium (Ru). The thickness of the capping layer 129 may be in the range of approximately 2 nm to 4 nm. The cover layer 129 may protect the reflective multilayer 120 during the manufacture of the absorber pattern 130. According to another embodiment, the capping layer 129 may be a titanium oxide (TiO) layer.

The substrate 110 may include a conductive interface layer 119 between the reflective multilayer 120 and the main portion 115 of the substrate. For example, the conductive interface layer 119 may be a metal containing tantalum (Ta) or chromium (Cr) or composed of tantalum (Ta) or chromium (Cr). membrane. The conductive interface layer 119 may at least partially connect a part of the reflective multilayer 120 in the pattern portion 191 with the frame portion 192, and may prevent the pattern portion 211 from being charged-up during exposure, thereby making the exposure free from electrostatic charges. Influence.

The frame trench 180 may extend down to the upper edge of the conductive interface layer 119, may extend into the conductive interface layer 119, or may partially perforate the conductive interface layer 119, wherein residues of the conductive interface layer 119 may be in the pattern portion 191 and the frame A bridge is formed between the parts 192.

In FIG. 3A, the protective structure 200 is a single layer directly bonded or deposited on the surface of the main portion 115 of the substrate. The bonding between the directly bonded protective structure 200 and the main substrate 115 may be based on chemical bonds, hydrogen bonds, metal bonds, ionic bonds and/or covalent bonds between the main substrate 115 and the protective structure 200. Direct bonding may include applying a moderate mechanical force to squeeze the protective structure 200 and the photomask 100, and at least one of the two bonding surfaces is heat-treated at a moderate temperature lower than 120°C (for example, lower than 100°C) , Or heat treatment for the combination of the two bonding surfaces, such as fusion bonding, thermo-compressive bonding or bonding by atomic rearrangement. Direct bonding may include the absence of any additional intermediate layers, especially the absence of resin-containing adhesives.

Alternatively, the protective structure 120 may be deposited (for example sprayed) on the exposed surface of the main portion 115 of the substrate, wherein the formation of the protective structure 120 may include baking spraying at a moderate temperature lower than 120°C (for example lower than 110°C) The protective structure 120 to remove volatile substances.

In FIG. 3B, the protective structure 200 includes a rigid main carrier 230 and an adhesive layer 220 for adhering the rigid main carrier 230 to the main part 115 of the substrate of the reflective photomask 100. The main carrier 230 may include a plate or frame, and the plate or frame includes at least one of glass, metal, semiconductor material (such as crystal or polysilicon), ceramic, silicon oxide, sintered material, and rigid resist.

The adhesive layer 220 reversibly bonds the main carrier 230 and the main substrate 110. For example, the adhesive layer 220 includes glue, adhesive film and/or adhesive foil. The adhesion layer 220 may include, for example, polyacrylate.

In FIG. 3C, the protective structure 200 includes a flexible tape 240 and an adhesive layer 220 that reversibly bonds the flexible tape 240 to the main portion 115 of the substrate. For example, the flexible tape 240 may include polyolefin (polyolefine), polyethylene (polyethylene, PET), or polyvinyl chloride (polyvinyl chloride, PVC), or may be made of polyolefin (polyolefine), polyethylene (polyethylene, PET) Or it is composed of polyvinyl chloride (PVC). For example, the thickness of the flexible tape may be in the range of 60 μm to 100 μm. The adhesive layer 220 may include an adhesive foil.

4A to 4C relate to the reflective photomask 100, the substrate 110 of which includes a backside film 114. The protective structure 200 is directly formed on the surface of the backside film 114. The backside film 114 may include a conductive layer (for example, a chromium nitride (CrN) layer). For more details about the protective structure 200 and the photomask 100, please refer to the foregoing description and drawings.

FIGS. 5A to 5B show a mechanical adaptor 300. The mechanical adaptor 300 has a rectangular receiving port 310 suitable for supporting the reflective optical cover 100. The receiving port 310 may be formed on the top of the mechanical adapter 300 Grooves in the surface. The lateral dimensions d2 and d3 of the receiving port 310 may be equal to or slightly larger than the lateral dimension of the reflective mask 100.

The contour 303 of the mechanical adapter 300 may be equal to or approximate to the contour of a standard semiconductor wafer. For example, the mechanical adapter 300 may be a circle with a radius r1 of 150 mm. For tools designed to apply temporary carriers, backgrinding tape, dicing tape, or pick-up tape to semiconductor wafers (e.g., for laminating tools), enter the receiving port 310 The mechanical adapter 300 charged with the reflective photomask 100 can emulate the existence of a semiconductor wafer.

Figures 6A to 6D illustrate the use of the protective structure 200 in the manufacturing method of the reflective photomask 100, in which the reflective photomask 100 and the unpatterned absorber layer stack 134 are in the processing stage in the state of the mask material. The protective structure 200 is coupled to the reflective photomask 100. Other embodiments may incorporate the protective structure 200 to the reflective photomask 100 at an earlier processing stage (for example, before depositing the absorber layer stack 134, or before forming the reflective multilayer 120).

The upper part of FIG. 6A shows the reflective photomask 100 with the substrate 110 including the backside film 114 formed on the surface on the backside of the main part 115 of the substrate. For more details of the reflective photomask 100, please refer to the description of the previous drawings. The lower part of FIG. 6A shows the protective structure 200 with the rigid main carrier 230. For example, the adhesive 221 is applied on the top surface of the main carrier 230 by dripping the adhesive or by adhering the adhesive foil. Alternatively, an adhesive may be applied on the exposed surface of the backside film 114 or on both the main carrier 230 and the backside film 114. Along the top surface of the main carrier 230 and along the exposed surface of the backside film 114, the protective structure 200 and the reflective photomask 100 are in contact with each other.

As shown in FIG. 6B, the adhesive 221 in FIG. 6A forms an adhesive layer 220 that bonds the main carrier 230 to the reflective photomask 100. The adhesive layer 220 and the main carrier 230 form a protective structure 200 for the back side of the reflective photomask 100. The reflective photomask 100 and the protective structure 200 form the photomask assembly 900 as described above. The processing on the front side of the reflective photomask 100 can be continued, for example, by patterning the absorber layer stack 134 and/or forming a frame groove.

FIG. 6C shows the absorber pattern 130 formed by the absorber layer stack 134 of FIG. 6B. Then, the protective structure 200 can be removed by ultraviolet radiation and mechanical peeling.

Fig. 6D shows the reflective mask 100 removed from the protective structure 200 of Fig. 6C.

A method of manufacturing a semiconductor device may include the following steps. A reflective photomask is provided. The reflective photomask includes a substrate, a reflective multilayer on the first substrate surface of the substrate, and an absorber pattern on the reflective multilayer on the front side of the reflective photomask; A protective structure is provided on the surface of the second substrate on the back side; in the ultra-ultraviolet lithography apparatus, the ultra-ultraviolet light reflected by the reflective photomask charged with the protective structure is used to expose the semiconductor; and the semiconductor substrate is exposed After that, the protective structure is removed. Before replacing the protective structure, more than one exposure can be performed, and the reflective mask can be installed in the ultra-ultraviolet lithography equipment more than once. For the details of the reflective photomask and the protective structure, please refer to the aforementioned parts and drawings.

100: reflective mask

101: The first major surface

102: second major surface

103: side surface

104: surface normal

105: surface part

110: substrate

111: The first substrate surface

112: Second substrate surface

120: reflective multilayer

121: first layer

122: second layer

130: absorber pattern

180: frame groove

200: Protective structure

203: side surface

900: Mask assembly

d1: thickness

Claims (17)

A photomask assembly includes: a reflective photomask (100), including a substrate (110), and a reflective multilayer (120). The substrate (110) is located on the front side of the reflective photomask (100). On a first substrate surface (111); and a protection structure (200) located on a second substrate surface (112) of the substrate (110) on the back side of the reflective photomask (100), wherein the protection The structure (200) can be separated from the reflective mask (100) at a temperature lower than 150°C. The photomask assembly according to the aforementioned claim, wherein the substrate (110) includes a backside film (114), and wherein the protective structure (200) is directly formed on the backside film (114). The photomask assembly according to any one of the preceding claims, wherein the protective structure (200) can be separated from the reflective photomask (100) by at least one of the following: applying a temperature between 110°C and 150°C Temperature, applying electromagnetic radiation, applying a peeling fluid configured to release the bond between the reflective mask (100) and the protective structure (200), and applying a moderate mechanical force. The photomask assembly according to claim 1 or 2, wherein the protective structure (200) includes a main carrier (230) and an adhesive layer (220), wherein the adhesive layer (220) combines the main carrier (230) To the reflective photomask (100). The photomask assembly according to claim 1 or 2, wherein The protective structure (200) includes a carrier tape (240) and an adhesive layer (220), wherein the adhesive layer (220) bonds the carrier tape (240) to the reflective mask (100). The photomask assembly according to claim 1 or 2, further comprising: a mechanical adapter (300), including a receiving port (310) adapted to support the reflective photomask (100), wherein the mechanical adapter (300) The profile (303) corresponds to the standard wafer profile. A method for manufacturing a reflective photomask, the method comprising: forming a reflective photomask (100), the reflective photomask (100) includes a substrate (110), and is located on a first substrate surface of the substrate (110) (111) on a reflective multilayer (120), and an absorber pattern (130) on the reflective multilayer (120) on the front side of the reflective mask (100); and forming the absorber pattern (130) Before, a protective structure (200) is combined on a second substrate surface (112) of the substrate (110) on the back side of the reflective photomask (100). The method according to claim 7, wherein the protective structure (200) can be separated from the reflective photomask (100) at a temperature lower than 150°C. The method according to claim 7 or 8, wherein before forming the reflective multilayer (120), the protective structure (200) is combined with the reflective mask (100). The method according to claim 7 or 8, wherein after forming the absorber pattern (130), the protective structure (200) is separated from the reflective mask (100). A photomask assembly includes: a reflective photomask (100), including a substrate (110), a reflective multilayer (120) on a first substrate surface (111) of the substrate (110), and An absorber layer pattern (130) on the reflective multilayer (120) on the front side of the reflective photomask (100); and a protective structure (200) located on the back side of the reflective photomask (100) On a second substrate surface (112) of the substrate (110), by applying a treatment solution that is inert to the absorber pattern (130), the protective structure (200) can be removed from the reflective photomask (100) Remove. The photomask assembly according to claim 11, wherein the reflective photomask (100) includes a backside film (114), and the backside film (114) is directly formed on the second substrate surface (112), and The protective structure (200) is directly formed on the back side film (114). The photomask assembly according to claim 11 or 12, wherein the protective structure (200) includes a material that is completely soluble in a solvent fluid. The photomask assembly according to claim 11 or 12, wherein the protective structure (200) is sprayed on the surface (112) of the second substrate. A method for manufacturing a reflective photomask, the method comprising: forming a reflective photomask (100), the reflective photomask (100) includes a substrate (110) and a front side of the reflective photomask (100) A reflective multilayer (120) on a first substrate surface (111) of the substrate (110); before forming an absorber pattern (130) on the reflective multilayer (120), a protective structure (200) is provided ) On a second substrate surface (112) of the substrate (110) on the back side of the reflective photomask (100); and After forming the absorber pattern (130), the protective structure (200) is removed. The method according to claim 15, wherein the protective structure (200) is removed from the reflective photomask at a temperature of at most 150°C and/or by applying a treatment liquid that is inert to the absorber pattern (130) (100) Remove. The method according to claim 15, wherein the protective structure (200) is detached from the reflective mask (100).

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